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    let num1 = 123, num2 = 'hello';
    console.log(num1);
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    console.log(typeof(num1));  //打印数据类型
    console.log(typeof(num2));
    console.log('------------');
    let flag = true;
    console.log(flag);
    console.log(typeof(flag));
    flag = false;
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    console.log(typeof(flag));
    console.log('------------');
    let str1 = '子曰：“学而时习之”';
    console.log(str1);
    console.log(typeof(str1));
    //子曰：'学而时习之';
    //he said:'day day study';
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